The present invention relates to a system for loading, processing and unloading substrates, such as wafers, which are arranged on a carrier in a reactor, such as an oven comprising feed means for the said substrates, a transport surface, such as a turntable, an introduction device for the said reactor as well as removal means for the said substrates.
A system of this kind is known from U.S. Pat. No. 5,407,449 in the name of Zinger. In the structure described in that patent, at most three carriers (boats) are arranged on a rotary table. A carrier is situated in front of the gaslock which seals off the chamber in which the reactor is arranged from the environment. Wafers are fed through this gaslock to a carrier placed in front of it. After the carrier has been filled, it is moved on one position to beneath an oven and placed in the oven using a lifting device. Processing then takes place in the oven and after the lifting device has removed the carrier and replaced it on the transport surface, i.e. the turntable, the carrier with wafers is allowed to cool. The carrier is then moved to a following position and is again situated in front of the gaslock, where it can be emptied and refilled.
In this way, the actual processing time in the oven determines the passage in the system, i.e. there is sufficient time while processing a carrier in the over to allow another carrier to be unloaded and reloaded whale a subsequent carrier, with the wafers present therein, is allowed to cool gradually under optimum conditions.
In this way, it is possible to achieve a particularly high capacity for a single oven.
Although a system of this kind is advantageous, for certain applications it is moreover required that the heat distribution through the wafers be as uniform as possible during the processing in the oven while, moreover, an optimum distribution of the process gas becomes critical. In order to satisfy these various requirements, it is proposed to arrange the wafers, together with the carrier, in a rotating manner. With the structure according to the U.S. Pat. No. 5,421,892 this causes a handling problem.
The object of the present invention is, in the system according to the U.S. Pat. No. 5,407,449, to arrange the carriers rotatably in the oven while the complex fixed connection between carrier and the electric motor, as described in U.S. Pat. No. 5,421,892, is avoided.
This object is achieved in a system as described above in that said carrier is provided with a door plate for the said reactor being connected to said carrier, a fixedly arranged drive motor being present for rotational movement of the said carrier, as well as coupling means for bringing about and interrupting the said rotating connection between drive motor and carrier.
The invention is based on the idea of not connecting the door plate to the lifting device permanently, as in U.S. Pat. No. 5,421,892. In the device according to the invention, the door plate with carrier is provided with semiconductor wafers before it is introduced into the oven, and then the unit filled in this way is introduced into the oven using the known lifting device, coupling taking place in any form using a rotating connection. The unit comprising carrier and door plate is then removed from the oven and allowed to cool, and subsequently the carrier is emptied. However, in the meantime, a door plate/carrier unit which has meanwhile been filled can be placed in the oven. In this way, it is possible to work particularly quickly and efficiently. Owing to the longer residence time of the door plate outside the oven, the door plate will heat up less rapidly and there is less need for drastic measures to be taken in order to ensure that there is a seal between oven and door plate.
The rotary drive of the carrier can basically be realized in two ways. Firstly, the carrier may be arranged in a rotary manner in the door plate, as is known per se from U.S. Pat. No. 5,421,892. The carrier is then driven by coupling to the lifting means which move the door plate with carrier into the oven and in which lifting means there is a rotary drive for the carrier. This rotary drive may even be arranged outside the chamber in which the processing operations take place.
According to another approach, the door plate is arranged rotatably in the oven and after it has been closed against the oven the door plate is set in rotary motion. In this case, of course, the carrier is mounted in a fixed position in the door plate.